OMAP5910 USB Hardware Considerations
14-120
14.10.6
UART1 Connectivity when CONF_MOD_USB_HOST_HMC_MODE_R = 2, 10,
18, and 24
The USB signal multiplexing provides modes that allow UART1 signals to be
brought to OMAP5910 pins. This multiplexing is separate from UART1 multi-
plexing that is provided by OMAP5910 top-level pin multiplexing. When
CONF_MOD_USB_HOST_HMC_MODE_R is set to 2, 10, 18, or 24, three
signals to/from UART1 are provided to OMAP5910 pins when the OMAP5910
top-level pin multiplexing for those pins selects the USB signal multiplexer.
These signal assignments are described in Table 14–69.
Table 14–69. CONF_MOD_USB_HOST_HMC_MODE_R = 2, 10, 18, and 24 UART Signal
Assignments
OMAP5910 Pin Name
Signal Name
Direction
MCSI1.DOUT/USB1.TXD
UART1_TX
Output
MCSI1.BLK/USB1.VM
UART1_RX
Input
MCSI1.DIN/USB1.RCV
UART1_CTS
Input
14.10.7
MPU_BOOT Signal Sharing
The OMAP5910 device implements shared functionality on the MPU_BOOT/
USB1.SUSP pin. The MPU_BOOT pin is sampled at hardware reset. If low, the
MPU processor boots from memory connected to CS0 on the EMIFS; if high,
the MPU processor enters the boot overlay mode, causing it to boot from
memory connected to CS3 on the EMIFS. After reset, the pin may be config-
ured for other functionality, such as the USB1.SUSP output. The MPU_BOOT
signal has an internal pulldown resistor that is enabled by default. The boot
overlay mode requires an external pullup resister. The internal pulldown can
be disabled in the OMAP configuration registers.
14.10.8
USB D+, D– Pulldown for USB Function Controller
System implementations which use the OMAP5910 USB function controller
and are sensitive to supply current requirements may wish to implement weak
pulldown resistors on the USB D+ and D– signals associated with the USB
Type B receptacle. When there is no host controller attached upstream of the
USB Type B receptacle, the undriven D+ and D– wires can float to voltages
that cause excessive current consumption by the USB transceiver. Weak pull-
downs can help prevent this problem. Selection of pulldown resistor depends
on transceiver characteristics, and board layout and must be designed to meet
USB D+ and D– signal requirements.